1. Field of the Invention
The present invention relates to a method and apparatus for determining a transmission line for message transmission and reception in a network system.
2. Description of the Related Art
In a network wherein a plurality of LANs (Local Area Networks) are connected to each other through a plurality of WANs (Wide Area Networks) by a plurality of LAN connector units, a plurality of transmission lines capable of transmitting a message from a station of one LAN to a station of another LAN are generally available. One of the available transmission lines must therefore be determined.
A transmission line to be determined should not have any failure interval and must have a minimum load in its use as determination conditions. When a transmission line which satisfies these two determination conditions is selected, complicated processing is required. A special network monitor unit must be arranged independently of LAN connector units. For this reason, the system configuration becomes complicated, thus resulting in an expensive network system.
In order to transmit and receive a message between stations through a predetermined transmission line, an address (station address) of a station and an address (bridge port address) of a LAN (WAN) interface in a LAN connector unit indirectly connected to this station and constituting part of this transmission line must be paired. This address pair are generally registered in an address translation (AT) table by a hash method or the like. When a message is transmitted from station to station by broadcast, or when its response is performed, the address pair are automatically updated.